Ki Jeong Kim

Tobacco Tsip1, a DnaJ-Type Zn Finger Protein, Is Recruited to and Potentiates Tsi1-Mediated Transcriptional Activation

Tobacco stress-induced1 (Tsi1) is an ethylene-responsive-element binding protein/APETALA2–type transcription factor that plays an important role in both biotic and abiotic stress signaling pathways. We show that Tsi1-interacting protein1 (Tsip1), a DnaJ-type Zn finger protein, interacts with Tsi1 in vitro and in yeast (Saccharomyces cerevisiae). The transcript level of Tsip1 in tobacco (Nicotiana tabacum) increased upon treatment with salicylic acid (SA), ethylene, gibberellic acid, NaCl, and virus challenge. Tsip1 appeared to be physically associated with the chloroplast surface but dissociated from it after SA treatment. Tsip1 colocalized and coimmunoprecipitated with Tsi1 in plant cells following SA treatment. Tsip1 expression increased Tsi1-mediated transcription and was able to functionally compensate for loss of the Tsi1 transcriptional activation domain through a direct interaction with Tsi1. Transgenic plants simultaneously coexpressing Tsi1 and Tsip1 displayed stronger pathogen resistance and salt tolerance than did transgenic plants expressing either Tsi1 or Tsip1 alone. Concurrent with this, the expression of a subset of stress-related genes was induced in a cooperative manner in Tsi1/Tsip1 transgenic plants. These results together implied that Tsi1 recruits Tsip1 to the promoters of stress-related genes to potentiate Tsi1-mediated transcriptional activation.

A hot pepper gene encoding WRKY transcription factor is induced during hypersensitive response to Tobacco mosaic virus and Xanthomonas campestris

Plant WRKY transcription factors were previously implicated in the alteration of gene expression in response to various pathogens. The WRKY proteins constitute a large family of plant transcription factors, whose precise functions have yet to be elucidated. Using a domain-specific differential display procedure, we isolated a WRKY gene, which is rapidly induced during an incompatible interaction between hot pepper and Tobacco mosaic virus (TMV) or Xanthomonas campestris pv . vesicatoria (Xcv). The full-length cDNA of CaWRKY-a (Capsicum annuum WRKY-a) encodes a putative polypeptide of 546 amino acids, containing two WRKY domains with a zinc finger motif. The expression of CaWRKY-a could be rapidly induced by not only chemical elicitor such as salicylic acid (SA) or ethephon but also wounding treatments. The nuclear localization of CaWRKY-a was determined in transient expression system using tobacco BY-2 cells by polyethylene glycol (PEG)-mediated transformation experiment. With oligonucleotide molecules containing the putative W-box sequences as a probe, we confirmed that CaWRKY-a protein had W-box-binding activity. These results suggest that CaWRKY-a might be involved as a transcription factor in plant defense-related signal transduction pathways.

GDSL-lipase1 (CaGL1) contributes to wound stress resistance by modulation of CaPR-4 expression in hot pepper

A full length cDNA clone encoding Capsicum annuum GDSL-lipase 1 (CaGL1) was isolated by microarray analysis. The expression of CaGL1 was triggered by methyl jasmonic acid (MeJA), an important signal in abiotic/biotic stress response. However, the expression of this gene was not increased by the application of salicylic acid (SA) or ethylene treatment. And, local/systemic wounding stimuli resulted in rapid accumulation of CaGL1 mRNA. However, CaGL1 was not specifically induced during the hypersensitive response upon Tobacco mosaic virus (TMV) inoculation. By using a virus-induced gene silencing (VIGS)-based reverse genetic approach, it was observed that the suppression of CaGL1 attenuates the expression of Capsicum annuumpathogenesis-related protein 4 (CaPR-4) during wound stress. However, the CaPR-4 transcript level induced by TMV was not regulated by CaGL1 expression. These results indicate that CaGL1 may be involved in signaling pathway of MeJA and/or the wound responses through CaPR-4 expression modulation.

Capsicum annuum basic transcription factor 3 (CaBtf3) regulates transcription of pathogenesis-related genes during hypersensitive response upon Tobacco mosaic virus infection

Hypersensitive response (HR) cell death upon plant virus infection is an excellent plant strategy for inhibiting viral movement and obtaining systemic acquired resistance (SAR) against further infection. Various host factors are involved in these HR processes, either directly as viral resistance proteins or indirectly. We characterized a gene encoding the CaBtf3 [β-nascent polypeptide-associated complex (NAC) subunit] of NAC from the hot pepper plant. NAC contacts nascent polypeptides to prevent aggregation and degradation of newly synthesized proteins by controlling cotranslational protein folding. CaBtf3 protein fused to green fluorescent protein predominantly localized to the nucleus. Silencing phenotype of CaBtf3 upon the Tobacco mosaic virus (TMV)-P(0) inoculation exhibited reduced HR cell death and decreased expression of some HR-associated genes, but increased TMV coat protein levels compared with TRV2 control plants. Furthermore, silencing of NbBtf3, a highly homologous gene of CaBtf3, also led to the reduced Bax- and Pto-mediated cell death. The results indicate that CaBtf3 might be involved in HR cell death and could function as a transcription factor in the nucleus by transcriptional regulation of HR-related gene expression.

CaAlaAT1 catalyzes the alanine: 2-oxoglutarate aminotransferase reaction during the resistance response against Tobacco mosaic virus in hot pepper

Hot pepper (Capsicum annuum L. cv. Bugang) plants exhibit a hypersensitive response (HR) upon infection by Tobacco mosaic virus (TMV) pathotype P0. To elucidate molecular mechanism that underlies this resistance, hot pepper cv. Bugang leaves were inoculated with TMV-P0 and genes specifically up-regulated during the HR were isolated by differential screening. One of the clones, CaAlaAT1 encoding a putative alanine aminotransferase (EC 2.6.1.2) exhibited organ-specific expression pattern and the transcript accumulated abundantly in red (ripe) fruit tissues. CaAlaAT1 transcript was also induced in older leaves during senescence. The expression of CaAlaAT1 gene was increased in the incompatible interaction with TMV-P0 but was not in the compatible interaction with TMV-P1.2. When a strain of Xanthomonas campestris pv. vesicatoria (Xcv) carrying an AvrBs2 gene was infiltrated into the leaves of a pepper cv. ECW 20R carrying Bs2 resistance gene, a marked induction and maintenance of CaAlaAT1 gene expression was observed. The expression of CaAlaAT1 gene was triggered by salicylic acid (SA) and ethylene but not by methyl jasmonate (MeJA). CaAlaAT1 seemed to be localized mostly at the cytosol from the polyethylene glycol (PEG)-mediated transformation experiment. CaAlaAT1 seemed to catalyze alanine: 2-oxoglutarate aminotransferase (AKT) reaction, which was a main activity among the four activities in vitro, during the resistance response against TMV in hot pepper. These results suggest that CaAlaAT1, a protein known to be involved in metabolic reactions, might be one of the components in the plant’s defense signal pathway against pathogens.

Induction of a cytosolic pyruvate kinase 1 gene during the resistance response to Tobacco mosaic virus in Capsicum annuum

Hot pepper (Capsicum annuum L. cv. Bugang) plants exhibit a hypersensitive response (HR) upon infection by Tobacco mosaic virus (TMV) pathotype P0. Previously, to elucidate molecular mechanism that underlies this resistance, hot pepper cv. Bugang leaves were inoculated with TMV-P0 and genes specifically up-regulated during the HR were isolated by microarray analysis. One of the clones, Capsicum annuum cytosolic pyruvate kinase 1 (CaPKc1) gene was increased specifically in the incompatible interaction with TMV-P0. The expression of CaPKc1 gene was also triggered not only by various hormones such as salicylic acid (SA), ethylene, and methyl jasmonate (MeJA), but also NaCl and wounding. These results suggest that CaPKc1 responds to several defense-related abiotic stresses in addition to TMV infection.

Pathogen-inducible CaUGT1 is involved in resistance response against TMV infection by controlling salicylic acid accumulation.

Capsicum annuum L. Bugang exhibits a hypersensitive response against Tobacco mosaic virus (TMV) P0 infection. The C. annuum UDP‐glucosyltransferase 1 (CaUGT1) gene was upregulated during resistance response to TMV and by salicylic acid, ethephon, methyl viologen, and sodium nitroprusside treatment. When the gene was downregulated by virus‐induced gene silencing, a delayed HR was observed. In addition, free and total SA concentrations in the CaUGT1‐downregulated hot pepper were decreased by 52% and 48% compared to that of the control plants, respectively. This suggested that the CaUGT1 gene was involved in resistance response against TMV infection by controlling the accumulation of SA.

Erratum: A hot pepper cDNA encoding ascorbate peroxidase is induced during the incompatible interaction with virus and bacteria (Molecules and Cells (2002) 14 (75-84)

Retraction Note: Mol. Cells 14 (2002) 75–84 Members of the editorial board have unanimously agreed to retract the article [Mol. Cells 14 (2002) 75–84] for potential misconducts mainly concerning manipulation and repeated uses of photomicrographs of control data internally along with mislabeling and/or externally in multiple publications. As specified in the “Instructions to Authors”, Molecules and Cells (Mol. Cells) explicitly prohibits mis-representation or falsification of experimental data including duplication of previously published data. In the article, lanes 1-6 and Lanes 10–15 of EtBr gel of rRNA in Fig. 5 are mirror images of each other; a part of this image has been previously used in Fig. 4B of Mol. Cells 11 (2001) 122–127; this image has also been used in Fig. 2D of Plant Physiol. 135 (2004) 561–573; rRNA gels in Figs. 6A, 6B, and 6C are identical, and rRNA gels in Figs. 7A and 7B are identical as well.